Multi-chips module package and manufacturing method thereof

ABSTRACT

A multi-chips module package comprises a lead frame, a first chip, a second chip, a plurality of electrically conductive wires and an encapsulation. The lead frame has a plurality of first leads, second leads and chip pads connecting to the first leads. The first chip is placed on the lead frame and electrically connected to the lead frame through the bumps connecting the bump-bonding pads and the chip pads and the first leads; the second chip is placed over the first chip and electrically connected to the lead frame through the wires connecting the wire-bonding pads to the second leads; and the encapsulation covers the first chip, the second chip, the lead frame, and the wires. In such a manner, it not only reduces the distance of transmitting the electrical signals from chips to the outside but also it can save cost due to the lead frame manufactured by a simple manufacturing processes. In addition, a manufacturing method of the multi-chips module package is provided.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a multi-chips module package. Moreparticularly, the present invention is related to a multi-chips modulepackage for integrating wire-bonded chip and flip chip therein and amanufacturing method thereof.

2. Related Art

As we know, in the semiconductor industries, the manufacture ofsemiconductors mainly comprises the manufacture of wafers and theassembly of integrated circuits devices. Therein, the integratedcircuits (ICs) devices are completely formed by the processes of formingintegrated circuits devices on the semiconductor wafers, sawing thewafers into individual integrated circuits devices, placing theindividual integrated circuits devices on the substrates, electricallyconnecting the integrated circuits devices to the substratesrespectively and encapsulating the integrated circuits devices andsubstrates to form a plurality of individual assembly packages. Due tothe encapsulation covering the integrated circuits devices, theintegrated circuits devices are able to be protected from the dampentering therein. In addition, the individual assembly packages mayfurther provide external terminals for connecting to printed circuitboard (PCB).

However, recently, integrated circuits packaging technology is becominga limiting factor for the development in packaging integrated circuitsdevices of higher performance. Semiconductor package designers arestruggling to keep pace with the increase in pin count, sizelimitations, low profile, and other evolving requirements for packagingand mounting integrated circuits.

Due to the assembly package in miniature and the integrated circuitsoperation in high frequency, MCM (multi-chips module) packages arecommonly used in said assembly packages and electronic devices. Usually,said MCM package mainly comprising at least two chips encapsulatedtherein is provided, for example a processor unit, a memory unit andrelated logic units, to upgrade the electrical performance of saidassembly package. In addition, the electrical paths between the chips insaid MCM package are short so as to reduce the signal delay and save thereading and writing time.

Generally speaking, as shown in FIG. 1, it illustrates a cross-sectionalview of a conventional multi-chips module package. Therein, saidmulti-chips module package 100 mainly comprises two chips 10 and 12, asubstrate 16, an encapsulation 18, a plurality of electricallyconductive wires 19. The substrate 16 has an upper surface for carryingthe chips 10 and 12 which are located in parallel, and the chips 10 and12 are electrically connected to the substrate 16 through said wires 19.In addition, the encapsulation 18 covers the chips 10 and 12, said wires19 and a portion of the substrate 16. Hence, the area of the substrate16 will be increased according to the numbers of the chips to be carriedthereon so as to make the complete package larger and larger.

Accordingly, the semiconductor industries develop a stacked multi-chipspackage as shown in FIG. 2, which illustrates that the package mainlycomprises a first chip 28, a second chip 26 and a substrate 20. Therein,the first chip is attached to the substrate 20 via an adhesive layer(not shown) and the second chip 26 is mounted onto the first chip 28.Besides, the upper surface of the substrate 20 further has a pluralityof wire-bonding pads 22 and 24, and the first chip 28 and the secondchip 26 are electrically connected to the substrate 20 through aplurality wires 29 wire-bonding to the wire-bond pads 22 and 24respectively. Thus, the electrical signals can be transmitted to theexternal electronic devices, such as printed circuit boards, through aplurality of solder balls attached to the lower surface of the substrate20. Moreover, an encapsulation 28 is formed to cover the first chip 28and the second chip 26 to well protect the chips 26 and 28 from beingmoisture entering into the chips 26 and 28 to cause the chips 26 and 28damaged.

Furthermore, as shown in FIG. 3, it illustrates a multi-chips stackedpackage patented in U.S. Pat. No. 5,973,403 to James M. Wark et.alentitled “Device and Method for stacking wire-bonded integrated circuitdice on flip-chip bonded integrated circuit dice” and said stackedpackage mainly comprises a flip chip 48, a wire-bonded chip 46, and asubstrate 40. The flip chip 48 is bonded to the upper surface of thesubstrate 40 through a plurality of bumps 52 formed on the flip chip 48connecting to the flip-chip pads 44 formed on the substrate 40; and thewire-bonded chip 46 is mounted to the back surface of the flip chip 48and electrically connected to the wire-bonded pads 42 formed on thesubstrate 40. To be noted, the bumps 47 are formed on the flip chip 48through typical bumping process and said bumps 47 can be solder bumps orgold bumps. Moreover, an encapsulation 49 is formed to cover thewire-bonded chip 46 and the flip chip 48 to well protect the chips 46and 48 from being moisture entering into the chips 46 and 48 to causethe chips 46 and 48 damaged.

As mentioned above, the layout of the circuits arranged in the substrateapplicable to such package as shown above is so complex that the cost ofsubstrate is very expensive due to the complexity of manufacturingsubstrate. Moreover, the electrical traces are longer so that theimpedance, the inductance and the noise will be increased to lower theelectrical performance.

Moreover, a multi-chips stacked package patented in U.S. Pat. No.5,973,403 to Lo et.al entitled “Flip Chip Type Quad Flat Non-LeadedPackage” is incorporated into this application for reference. Therein,it discloses a flip chip package which mainly comprises a plurality ofleads for taking as electrical terminals for electrically connecting thechip and the external electronic devices. To be noted, the leads havefirst surfaces and second surfaces, and the chip are bonded to the firstsurfaces through a plurality of bumps and the second surfaces areexposed out of the encapsulation to connect to said external electronicdevices as mentioned above. However, the leads are easily separated fromthe encapsulation so as to be not able to well connect to externalelectronic devices.

Therefore, providing another multi-chips module package andmanufacturing method thereof to solve the mentioned-above disadvantagesis the most important task in this invention.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, the invention is to provide amulti-chips module package for integrating wire-bonded chip and flipchip therein and a manufacturing method thereof.

To achieve the above-mentioned, a multi-chips module package isprovided, wherein the multi-chips module package mainly comprises a leadframe, a first chip, a second chip, a plurality of electricallyconductive wires and an encapsulation. Therein, the lead frame has aplurality of first leads, second leads and chip pads connecting to thefirst leads; the first chip has a first active surface, a first backsurface opposite to the first active surface, bump-bonding pads formedon the first active surface, wherein the first chip is placed on thelead frame and electrically connected to the lead frame through thebumps connecting the bump-bonding pads and the chip pads and the firstleads; the second chip has a second active surface, a second backsurface opposite to the second active surface, wire-bonding pads formedon the second active surface, wherein the second chip is placed over thefirst chip and electrically connected to the lead frame through thewires connecting the wire-bonding pads to the second leads; and theencapsulation covers the first chip, the second chip, the lead frame,and the wires.

Per this invention and mentioned above, the leads of the lead frame mayhave recesses formed thereon or the leads may have flat surfaces. Inaddition, the chip pads may have recesses for locking the bumps on thechip pads securely and takes as power connections or ground connections.

In summary, this invention is related to a multi-chips module packagewith a lead frame therein for electrically connecting the first chip andthe second chip to external electronic devices. In such a manner, it notonly reduces the distance of transmitting the electrical signals fromchips to the outside so as to enhance electrical performance but also itcan save cost due to the lead frame manufactured by a simplemanufacturing processes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the detaileddescription given herein below illustrations only, and thus are notlimitative of the present invention, and wherein:

FIG. 1 is a cross-sectional view of the conventional multi-chips modulepackage in a side-by-side type;

FIG. 2 is a cross-sectional view of another conventional multi-chipsmodule package in a stacked type;

FIG. 3 is a cross-sectional view of another conventional multi-chipsmodule package;

FIG. 4 is a cross-sectional view of multi-chips module package accordingto the first preferred embodiment of this invention;

FIG. 5 is a bottom view of multi-chips module package according to thefirst preferred embodiment of this invention as shown in FIG. 4;

FIG. 6 is a top view of the lead frame strip having a plurality of leadframes being provided in the multi-chips module package according to thefirst preferred embodiment of this invention of FIG. 4;

FIG. 7 is a cross-sectional view along line 7-7′ of the lead frameaccording to the first preferred embodiment of this invention of FIG. 6;

FIG. 8 is a cross-sectional view along line 8-8′ of the lead frameaccording to the first preferred embodiment of this invention of FIG. 6;

FIG. 9 is a cross-sectional view of the lead frame after the lead frameof FIG. 7 is performed half-etched process;

FIG. 10 is a cross-sectional view of the lead frame after the lead frameof FIG. 8 is performed half-etched process;

FIG. 11 is a cross-sectional view of a semi-finished multi-chips modulepackage before encapsulating according to the first preferred embodimentof this invention;

FIG. 12 is a three-dimensional figure illustrating a semi-finishedmulti-chips module package before encapsulating according to the firstpreferred embodiment of this invention;

FIG. 13 is a schematic figure illustrating a semi-finished multi-chipsmodule package with a tape attached thereto after encapsulatingaccording to the first preferred embodiment of this invention;

FIG. 14 is a cross-sectional view of multi-chips module packageaccording to the second preferred embodiment of this invention;

FIG. 15 is a cross-sectional view of multi-chips module packageaccording to the third preferred embodiment of this invention;

FIG. 16 is a bottom view of multi-chips module package according to thethird preferred embodiment of this invention of FIG. 15; and

FIG. 17 is a three-dimensional figure illustrating a semi-finishedmulti-chips module package before encapsulating according to the thirdpreferred embodiment of this invention;

DETAILED DESCRIPTION OF THE INVENTION

The multi-chips module package according to the preferred embodiments ofthis invention will be described herein below with reference to theaccompanying drawings, wherein the same reference numbers refer to thesame elements.

FIGS. 4 and 5 are enlarged cross-sectional views showing thecross-sectional view of a multi-chips module package according to thefirst preferred embodiment of this invention.

As shown in FIG. 4, the multi-chips module package 100 mainly comprisesa first chip 110, a second chip 120 and a lead frame 130. Therein, thefirst chip 110 is flip-chip bonded to the lead fame 130 and the secondchip 120 is disposed on the first chip 110 and electrically connected tothe lead frame 130 through a plurality of electrically conductive wires.

To be noted, the lead frame 130 as mentioned above has a plurality ofleads 134, chip pads 142 and tie bars 143, wherein at least one of thechip pads 142 is connected to one of the leads 134 through thecorresponding tie bar 143 as shown in FIG. 4. Besides, the first chip110 has a plurality of bump-bonding pads 118 formed on the activesurface thereof and electrically connected to the leads 134 through aplurality of bumps 114 connecting to the chip pads 142 and the tie bars143 connecting the leads 134 and the chip pads 142; and the second chip120 is displace over the first chip 110, wherein the second chip 120 hasa plurality of wire-bonding pads 128 formed thereon and electricallyconnected to the leads 134 through wires 132 connecting said leads 134and the wire-bonding pads 128. Moreover, the encapsulation 140encapsulates the first chip 110, the second chip 120, the wires 132, thebumps 114 and the chip pads 142, and portions of the leads 134 which areexposed out of the encapsulation 140 so as to be served as electricalterminals for connecting to external electronic devices. To be noted,the tie bars 143 are encapsulated in the encapsulation 140.

Referring to FIGS. 6 to 13, which are partially enlarged cross-sectionalviews showing the progression of steps for forming a multi-chips modulepackage according to the first and other preferred embodiments of thisinvention.

As shown in FIG. 6, firstly, a lead frame strip 150 is provided, whereinthe lead frame strip 150 has a frame 154 supporting a plurality leadframes 130. Each lead frame 130 has a plurality of leads 134 arranged atthe four sides and connected to the frames 130 thereof. Each lead frame130 further has a plurality chip pads 142 and a plurality tie bars 143connecting the leads 134 to the corresponding chip pads 142. Each chippad 136 has a recess 136 for filling a solder material, such as solderpastes or epoxy pastes. To be noted, the chip pads 142 may be directlyconnected to the frame 154 instead of being connected to the frame 154through said leads 134.

Then, referring to FIGS. 7 and 8, typically, the lead frame strip 150has an equable thickness. In other words, each lead frame 130 hassubstantially the same thickness with each other. Afterwards, the leadframe strip 150 is etched to form reentrant portions 148, such as astepper, formed at the lower surfaces 146 of the lead frame 130 of thelead frame strip 150 as shown in FIGS. 9 and 10. The reentrant portions148 may have the encapsulation well locked with the lead frame 130 so asto prevent the moisture from entering into the package 100. Referring toFIG. 11, the first chip 110 has a first active surface 112, a first backsurface 113, a plurality of bumps 114, a plurality of bump-bonding pads118 located on the first active surface 112 and a plurality of underbump metallurgy layers 116 formed on the bump-bonding pads 118. To benoted, the bumps 114 are attached to the under bump metallurgy layers116 over the bump-bonding pads for electrically connecting to theoutside, such as leads or chip pads of the lead frame 130; and are madeof the materials of gold and solder materials. In addition, the bumps114 of the first chip 110 is aligned with the recesses 136 of the chippads 136 of the lead frame 130, and are secured to the chip pads 136through the performing reflowing process.

Furthermore, a second chip 120 has a second active surface 124 and asecond back surface 126, and the second chip 120 is attached to thefirst back surface 113 of the first chip 110 via an adhesive 127, suchas epoxy resin or silver paste.

Referring to FIG. 12, a plurality of electrically conductive wires 132are bonded to the wire-bonding pads 128 of the second chip 120 and theleads 134 of the lead frame 130. To be noted, the leads 134 have goldlayers 152 formed thereon for enhancing the connection of the wires 132with the leads 134.

Referring to FIG. 13, a plurality of taps or films 146 are attached tothe lower surfaces of the leads 134 to prevent the mold compound fromoverflowing the lower surfaces of the leads 134 when the encapsulationprocess is performed. Finally, when the encapsulation process iscompletely performed, the tapes or films 146 are removed to leave thelower surfaces of the leads 134 exposed out of the encapsulation 140 tocomplete said multi-chips module package 100 as shown in FIG. 4 and FIG.5.

Referring to FIG. 14, which illustrates another preferred embodiment ofthis invention. This embodiment shows a package 100′ similar with thefirst one as shown above. To be noted, the difference of this embodimentfrom the first one is that there is a bridge pad 122 formed on the firstback surface 113 of the firs chip 110. Therein, the second chip 120 andthe leads 134 are electrically connected through the first wire 132connecting the second chip 120 and the bridge pad 122 and the secondwire 132′ connecting the bridge pad 122 and the leads 134 so as toprevent the first wires and the second wires from being damaged due tothe mold compound's sweeping.

Referring to FIG. 15 and FIG. 16, which illustrate a second preferredembodiment of this invention. This embodiment shows a package 200similar with the first one as shown above. To be noted, the differenceof this embodiment from the first one is that the lead frame 130 has aco-connected chip pad 242 with a plurality of recesses 236 formedthereon for carrying the bumps 114 of the firs chip 110. In addition,the co-connected chip pad 242 further has a plurality of reentrantportions 248 for having the encapsulation well locked with the leadframe 130. Besides, the lower surface of the co-connected chip pad 242may be flat and exposed out of the encapsulation 140 for serving as aground terminal or a power terminal.

Referring to FIG. 17, which illustrates a third embodiment of thisinvention. This embodiment shows a package 300 similar with the firstembodiment as shown above. The chip pads 142 are connected to the leads134 in a longitudinal direction and the second chip 120 is electricallyconnected to gold layer 152 of the leads 134 in a transversal directionorthogonal to the longitudinal direction.

As mentioned above, in this package, the lead frame is utilized to carrythe chips, accordingly, it not only reduces the distance of transmittingthe electrical signals from chips to the outside so as to enhanceelectrical performance but also can save cost due to the lead framemanufactured by a simple manufacturing processes.

Although the invention has been described in considerable detail withreference to certain preferred embodiments, it will be appreciated andunderstood that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

1-17. (canceled)
 18. A manufacturing method of multi-chips modulepackages, comprising: providing a first chip, the chip having a firstactive surface, a first back surface and a plurality of bump-bondingpads formed on the first active surface; forming a plurality of bumpsover the bump-bonding pads; providing a second chip, the chip having asecond active surface, a second back surface and a plurality ofwire-bonding pads formed on the second active surface; providing a leadframe strip, the lead frame strip having a plurality of lead frame andsaid each lead frame having first leads, second leads and a plurality ofchip pads connecting to the first leads; placing the first chip over thechip pads and connecting the first chip and the chip pads through thebumps; placing the second chip over the first chip; providing aplurality of wires to connect the wire-bonding pads and the secondleads; forming an encapsulation to cover the first chip, the secondchip, the wires and the chip pads to form a plurality of semi-finishedmulti-chips module packages, wherein a portion of the first leads andthe second leads are exposed out of the encapsulation; and singulatingthe lead frame strip to have the semi-finished multi-chips modulepackages separated into a plurality of the multi-chips module packages.The method of claim 18, further comprising steps of: providing aplurality of tapes attached to the portions of the first leads and thesecond leads; and removing the taps to leave the portions of the firstleads and the second leads exposed out of the encapsulation afterperforming the step of forming an encapsulation.
 19. The method of claim18, further comprising a step of forming under bump metallurgy layers onthe bump-bonding pads.
 20. The method of claim 18, further comprising astep of etching the first leads and the second leads to form a pluralityof reentrant portions on the first leads and the second leads.
 21. Themethod of claim 18, further comprising a step of forming gold layers onthe second leads.
 22. The method of claim 18, further comprising a stepof forming gold layers on the second leads.
 23. The method of claim 18,further forming a recess on the chip pad.
 24. The method of claim 23,further filling a solder material in the recess. 25-30. (canceled)